A circuit arrangement is used for electrical consumers such as for instance a coil control or a switching power supply in conjunction with clocked electronic systems, which can transmit interference signals. Circuit arrangements for electromagnetic compatibility (EMC) are needed to eliminate interference signals of this type particularly in power networks, but also in other areas of application. The circuit arrangements are generally based on a capacitor with a large capacity, which is provided on supply lines, in particular at the input of the circuit to be protected in each instance. The capacitor is used here as a buffer or damper for possible current peaks, which originate from the clocked electronic system. An EMC circuit arrangement can be used as such separately in a module or integrated in a device.
The large capacity of the capacitor, which is used as a damping member, is always problematical if the mains power supply used only permits a limited current consumption. As the capacitor is connected to a supply line, when the device and/or consumer is switched on, into which a circuit arrangement is integrated or arranged upstream thereof, a high charging current develops shortly after switching-on in order to charge the capacitor. It is consequently always necessary to consider whether a capacitor with a large capacity is to be used as a result of the EMC, or whether the loading capacity of the grid, in terms of current, is to limit the capacity of the capacitor.
Inductors or current limiters were previously used in this context, which provided for the charging current in the supply line to be restricted to a tolerable minimum. The disadvantage of this solution lies in the limiting element being located in the energy circuit and permanent losses therefore being generated during operation of a consumer.
WO 2005/006519 A1 discloses a circuit arrangement for eliminating EMC interference of a direct current motor. A circuit arrangement is taught, which provides a damping member for eliminating EMC interference of the DC motor in the lines of the same.